1. Field of the Invention
The invention relates to a thin film magnetic head including an inductive magnetic transducer for use in at least recording, and a magnetic recording apparatus equipped with a thin film magnetic head.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head mounted on a magnetic recording apparatus (e.g., a hard disk drive) has been sought in accordance with an increase in a surface recording density of a magnetic recording medium (e.g., a hard disk). A longitudinal recording type and a perpendicular recording type, for example, are known as the recording types of the thin film magnetic head. The longitudinal recording type is designed to orient a signal magnetic field in the in-plane direction of the hard disk (i.e., the longitudinal direction thereof). The perpendicular recording type is designed to orient a signal magnetic field in a direction perpendicular to the surface of the hard disk. Although the longitudinal recording type is widely used at present, the perpendicular recording type rather than the longitudinal recording type can be regarded as promising in the future, taking into account market trends incident to an increase in the surface recording density of the hard disk. The reason is as follows. The perpendicular recording type can obtain the advantage that the hard disk having information recorded thereon is less susceptible to thermal fluctuations, as well as the advantage of being capable of ensuring a high linear recording density.
The thin film magnetic head of the perpendicular recording type includes a thin film coil which generates a magnetic flux; a magnetic pole layer which emits to the hard disk the magnetic flux generated by the thin film coil, the magnetic pole layer being located on the leading side of the thin film coil and extending rearward from an air bearing surface; and a write shield layer which prevents divergence of the magnetic flux emitted from the magnetic pole layer, the write shield layer being located on the trailing side of the thin film coil and extending rearward from the air bearing surface. This thin film magnetic head performs a recording operation in the following manner. A current is fed through the thin film coil so that the thin film coil generates a magnetic flux for recording. Then, the magnetic pole layer emits the magnetic flux to the hard disk. The magnetic flux generates a magnetic field for recording (i.e., a perpendicular magnetic field), and the recording magnetic field magnetizes the hard disk. In this manner, the thin film magnetic head magnetically records information on the hard disk. During the recording operation, the write shield layer takes in a divergent component of the magnetic flux emitted from the magnetic pole layer, thus preventing divergence of the magnetic flux, that is, an increase in a write width.
During the recording operation of the thin film magnetic head, a current is fed through the thin film coil in order that the thin film coil generates a magnetic flux, as mentioned above. Thus, the thin film coil produces heat, which is consequently prone to accumulate in and near the thin film coil in the thin film magnetic head. In this case, too large an amount of heat accumulating in the write shield layer causes thermal expansion of the write shield layer under the influence of thermal energy, thus causes considerable protrusion of the write shield layer beyond the air bearing surface, thus causes a collision of the write shield layer with the rotating hard disk, thus causes damage to the thin film magnetic head, and thus leads to an increase in the likelihood of the hard disk drive breaking down. From this viewpoint, the thin film magnetic head has to minimize the amount of heat accumulating in and near the write shield layer in order to reduce the amount of protrusion of the write shield layer for the purpose of ensuring the recording operation of the thin film magnetic head with stability and also preventing the occurrence of a breakdown of the hard disk drive.
However, it cannot be said that conventional thin film magnetic heads provide satisfactory solutions to heat accumulation in the write shield layer. Thus, considerable protrusion of the write shield layer can occur and cause damage to the thin film magnetic head, depending on conditions such as the amount of heat produced by the thin film coil or the coefficient of thermal expansion of the write shield layer. Therefore, the conventional thin film magnetic heads may still cause a breakdown of the hard disk drive. More recently, the amount of levitation of a head slider having the thin film magnetic head mounted thereto, namely, the distance between the air bearing surface of the thin film magnetic head and a recording surface of the hard disk, has been reduced to about 10 nm. Accordingly, the thin film magnetic head must minimize the amount of protrusion of the write shield layer in order to prevent the thin film magnetic head from colliding with the hard disk.
For example, techniques for reducing the amount of heat accumulating in the thin film magnetic head include the approach of utilizing a thermally conductive heat sink layer to dissipate heat and thereby prevent heat from accumulating in the thin film magnetic head. For example, a magnetic head including a thin film coil, a magnetic pole layer, and a heat sink layer, wherein the heat sink layer is disposed on the trailing side of the thin film coil, more specifically beside or over the magnetic pole layer is specifically known as a thin film magnetic head which the above-mentioned approach is applied to (e.g., see Japanese Unexamined Patent Application Publication No. 2003-085707). However, this type of thin film magnetic head still has room for improvement in prevention of a collision of the thin film magnetic head, taking into account the recent trend, specifically that the amount of levitation of the head slider is decreasing year by year as mentioned above.